Bacterial infections of the blood, not malaria, may be the biggest killer of children in sub-Saharan Africa, and many of the deaths could be prevented by simple vaccinations, researchers said on Wednesday.

Each year in sub-Saharan Africa, 4.6 million children under age 5 die - making it home to the highest child mortality rates in the world, according to the U.N. Children’s Fund (UNICEF). The vast majority of those deaths are not investigated.

In a study that challenges conventional wisdom about infant mortality in one of the world’s poorest regions, researchers found 26 percent of childhood hospital deaths in a rural area of the Kenyan coast were associated with bacterial invasions of the blood, or bacteremia.

That compared to a death rate of 22 percent for cases linked to malaria, the parasitic illness presumed by many doctors and health organizations to be the leading killer of children in the region.

“We found that community-acquired bacteremia was responsible for at least one-third of deaths in infants and one-quarter of deaths in children over one year of age,” the researchers said in the study, published in this week’s issue of The New England Journal of Medicine.

The researchers, led by James A. Berkley at the Centre for Geographic Medicine Research (Coast) in Kilifi, Kenya, said the finding highlights the need to overcome the political and financial barriers to widespread use of vaccination for bacterial diseases.

Two types of bacteria, for which vaccines are widely used in developed countries, probably account for a minimum of 482,000 deaths across sub-Saharan Africa each year, the research team said.

Health agencies haven’t recognized the problem, which may help explain why vaccination has not been a priority, they said.

“Invasive bacterial infection does not specifically appear on the basic lists provided by the WHO (World Health Organization) and other agencies regarding the major causes of death in children in sub-Saharan Africa,” they said.

Instead, those lists blame malnutrition, diarrhea, malaria, measles and HIV.

The findings are “both surprising and enlightening,” according to E. Kim Mulholland of the University of Melbourne and Richard Adegbola of the Medical Research Council Laboratories in Fajara, Gambia.

In an editorial in the medical journal, they said the estimate that a child has a 2.5 percent chance of developing bacteremia before age 5 may actually be low. The reason: many children in and around the rural area that was the focus of the study became ill and died without medical care.

“Prevention of deaths from these conditions rests with improvement in the living conditions of children, reduction in the high rates of malnutrition, improved recognition of illness requiring medical care, and more prompt treatment with antibiotics and lifesaving supportive measures,” they said.

They noted, however, that the vaccines that exist to prevent some of the infections can be expensive, and may not cover all the strains that typically infect the children.